Alimentary System Infections & Hepatitis - PDF

Alimentary system infections Rotavirus and Norwalk (Norovirus) virus Gastroenteritis Symptoms: – Vomiting and slightly fever – Watery diarrhea – Symptoms are gone in about 3-7 days Pathogenesis  The viruses infect the epithelium in the upper part of small intestine, causing cell death and decreased...

Alimentary system infections Rotavirus and Norwalk (Norovirus) virus Gastroenteritis Symptoms: – Vomiting and slightly fever – Watery diarrhea – Symptoms are gone in about 3-7 days Pathogenesis  The viruses infect the epithelium in the upper part of small intestine, causing cell death and decreased production of digestive enzymes Rotavirus and Norwalk virus Gastroentritis Epidemiology – Spread by oral-fecal route – Generally occur in winter (Children) Prevention – Handwashing, disinfectant use limit the spread of viruses – Attenuated vaccine (Rotavirus) approved in 1998, then withdraw the next year (Bowel obstruction) – No vaccine for Norwalk viruses Hepatitis Viral hepatitis is an infection of the liver hepatocytes by viruses. There are 5 known viruses that infect the liver. The 5 RNA viruses are: 1) Hepatitis A virus (HAV). 2) Hepatitis C virus (HCV), which was previously called NON-A NON-B until it was isolated. 3) Hepatitis D virus (HDV). 4) Hepatitis E virus (HEV). 5) Hepatitis G virus. There is 1 DNA virus called: 1) Hepatitis B virus (HBV) ABCDE, A = Anal, E = Enteric (Fecal oral route) BCD = Blood (parenteral) VIRAL HEPATITIS 1. Acute viral hepatitis  can be caused by all of these viruses.  Symptomatic, patient may develop jaundice  Elevation liver-function enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (GGT), and alkaline phosphatase. 2. Chronic viral hepatitis.  The parenterally (blood-to-blood) transmitted HBV, HCV  Is more difficult to diagnose because the patient is often asymptomatic with only an enlarged tender liver and mildly elevated liver function enzyme levels. Hepatitis Hepatitis A (HAV) Symptoms: Fatigue, fever, loss of appetite, nausea, darkcolored urine, clay-colored feces and jaundice Pathogenesis: – Following ingestion, the virus reach the liver – Replication and tissue damage – The virus released into bile – The virus eliminated with feces HAV Epidemiology: – Spread by fecal-oral route – Fecal contamination of hand, food and water – Children with HAV can eliminate the virus with their feces for several months after symptoms begin HAV Prevention and treatment –Inactivated vaccine available since 1995 –IgG to HAV as passive immunization of people exposed to virus –No antiviral is available, just supportive HBV Symptoms: – Similar to HAV, except that HBV tend to be more sever. Cause death in 1% - 10% of hospitalized cases. Causative agent The important HBV antigens are: – Surface antigen (HBsAg) – Core antigen (HBcAg) – Soluble component of core (HBeAg) HBV (Epidemiology) Spread mainly by blood or semen The virus circulate in the blood for many years Body fluid can be infectious / Sharing of needles by drug abusers Shared toothbrushes, razors or towels HBV antigen is usually present in saliva and breast milk Sexual intercourse is moderate to high risk HBV Pathogenesis: – Following entry, the virus carried to liver / blood stream – Replication in the liver – HBsAg appears in blood stream days or weeks after infection, before sign of liver damage – About 40% of chronic cases die from cirrhosis or liver cancer HBV (Prevention) First vaccine (HBsAg) approved in 1980 Infected new born injected at birth with HBIG Vaccination at one week, one month and six months of age Education of groups can prevent the disease No curative antiviral treatment are available, But improvement can achieved by injection of interferon and lamivudine Symptoms HCV – The same of A and B, except is milder – About 65% have no symptoms – Only 25% have jaundice Pathogenesis: – Spread mainly by blood – Infect the liver (incubation 2 – 6 weeks) – 80% develop chronic infection – Liver wax – After years cirrhosis and liver cancer develop in 1020% of patients HCV Epidemiology: – The same of HBV, except transmission by sexual intercourse is rare Prevention: – No vaccine available – No satisfactory treatment for chronic diseases – 30-50% are helped by interferon combined with ribavirin – Prolonged interferon treatment of the acute disease may prevent the chronic disease